<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    function foo(){
        +function(){
            alert(aaa)
        }()
       ;
    }
    function foo2(){
        alert(bbb)
    }

    try {
        foo();
    } catch (e){
//        console.log(e);
    }

</script>
</body>
</html>